1. Field of the Invention
The present invention relates to a novel fiber having a capability of forming a chelate with metalloid elements such as boron, germanium, arsenic, antimony, selenium, tellurium, etc. and compounds thereof, a process for producing the same, and a method for capturing metalloid elements or compounds thereof (hereinafter referred merely to as metalloid elements or metalloid element component, sometimes) using said fiber. This fiber can be widely utilized for purification of industrial water and agricultural water, cleaning of air, and recovery of metalloid elements, industrially, because of its efficient performance of selectively adsorbing a trace amount of metalloid elements and compounds thereof, which are present in water and a gas.
2. Description of the Prior Art
Boron and boron compounds as a kind of metalloid elements are widely distributed in the nature and are essential to the human body, however, it is confirmed that large uptake of them exhibits an adverse influence on the human body. The case considered to be an artificial pollution due to boron components contained in river and underground water has recently been reported so that there is a fear of an adverse influence on reuse of water and on agriculture. A trace amount of boron components are also present with dusts in the air, and it has also been reported that these boron components can cause defects when a semiconductor device is produced.
In addition to boron, arsenic and arsenic compounds are also harmful to human body and it is necessary to remove as possible from potable water and various exhaust gases in which arsenic and arsenic compounds are considered to be included. Furthermore, since germanium, antimony, selenium and tellurium are expensive elements, it is considered to be very effective, from an industrial point of view, to efficiently scavenge from various liquid waste and exhaust gas, which contain a trace amount of them.
The method for removing metalloid elements such as boron in water includes, for example, a method using a basic ion exchange resin. The present inventors confirmation made it clear that the performance of capturing metalloid elements is drastically lowered when other anions are present in a system to be treated because selective adsorption of the basic ion exchange resin to the metalloid elements such as boron are very poor.
On the other hand, a chelate resin with a performance of capturing boron components exists and a method for removing boron components contained in irrigation water using the chelate resin is also known. This chelate resin is a beads-like or granular, resin wherein aminopolyol groups are introduced into a polymer having a rigid three-dimensional crosslinked structure, such as styrene-divinylbenzene resin and phenol-aldehyde resin, and following problems are pointed out, that is, the capturing amount and rate of the boron components are small and the regenerating rate is also very small in case where the chelate resin containing captured boron components is regenerated.
Although the above-mentioned chelate resin exhibits a certain degree of an effect of removing or capturing the boron components contained in water, a rate of diffusion into the resin is slow and a specific surface area to be effectively utilized for forming a chelate with metalloid element is very small. Therefore, the chelate resin hardly exhibits a performance of removing (or capturing) a trace amount of the boron components contained in a gas (e.g. air, various exhaust gases, etc.) and can not be applied to use to which a high-degree removing treatment is required, for example, purification of a semiconductor device production apparatus. These facts become a serious problem in case where arsenic and compounds thereof, which are harmful to human body, are removed.
On the other hand, boron, germanium, selenium, tellurium, and antimony are useful elements for development of new materials for supporting current frontier industries, such as superconductive material, semiconductor material, neutron absorbing material, etc., and it is considered that these elements can be utilized, very effectively from an industrial point of view, if a technique capable of efficiently capturing these metalloid elements to obtain them in a concentrated state can be established.
Under these circumstances, the present invention has been accomplished. A first object of the present invention is to provide a chelate-forming fiber which has excellent performance of capturing metalloid and compounds thereof. A second object of the present invention is to provide a process for efficiently producing the chelate-forming fiber. A third object of the present invention is to provide a method for capturing metalloid elements and compounds thereof.